Petrophysical Characterization and Reservoir Quality Assessment of Field "D" in the Central Niger Delta Basin, Nigeria: An Integrated Well Log Analysis

Abstract

This study presents a comprehensive petrophysical characterisation and reservoir quality assessment of Field "D", located in the Central Niger Delta Basin, Nigeria, utilising well log data from three exploratory wells (OTIG 2, OTIG 7, and OTIG 9). Rigorous data quality control, calibration verification, and uncertainty propagation analyses were integrated into the workflow to ensure the reliability of computed petrophysical parameters. The study integrated gamma-ray, resistivity, density, and neutron log responses to evaluate key reservoir properties, including porosity, permeability, shale volume, fluid saturation, net-to-gross ratio, and transmissivity across three hydrocarbon-bearing sandstone reservoirs (Reservoirs A, B, and C). Sensitivity analyses and cross-validation against regional benchmarks were performed to validate the empirical models employed. The results indicate that the reservoirs exhibit good to excellent reservoir quality, with average porosity values ranging from 14% to 20%, permeability values exceeding 100 millidarcies (md), and hydrocarbon saturation values between 48% and 70%. The bulk volume water (BVW) analysis suggests that the reservoirs are at or near irreducible water saturation, indicating good hydrocarbon producibility. Stratigraphic correlation revealed that Reservoirs A, B, and C in well OTIG 2 may represent a continuous sand body, supported by consistent petrophysical parameters and similar depth intervals. The inherent limitations of the well log dataset, including depth-dependent resolution constraints and the absence of core calibration, are explicitly discussed to contextualize the uncertainty bounds of the interpreted results. The findings indicate that Field "D" possesses significant hydrocarbon accumulation potential, with reservoir parameters comparable to other productive fields in the Niger Delta. This study contributes to the growing body of knowledge on integrated well log interpretation techniques for reservoir characterisation in the Niger Delta Basin and provides valuable insights for reservoir management and development planning.